Weight-related problems including obesity, poor eating behaviors, inadequate physical activity, unhealthy weight control practices, and body dissatisfaction are very prevalent among young adults, and have adverse physical and psychosocial consequences. Obesity is one of the most significant public health problems in today's society. NIH and prominent researchers have called for longitudinal research that examines multiple environments with the potential to influence obesity and other weight-related problems. The proposed study, EAT 2010-2018: A longitudinal, multi-contextual study of weight-related problems, is responsive to these calls. The primary aim of this study is to identif longitudinal, multi-contextual predictors of weight-related problems in a diverse population-based sample of young people as they transition from adolescence to young adulthood. To accomplish this aim, the proposed study builds upon existing data collected on 2,793 adolescents in EAT 2010 as part of a previously funded R01 study. The study population includes a high percentage of young people from ethnic/racial minority (82%) and low-income backgrounds (71% qualified for free/reduced price school meals at baseline) who are at high risk for obesity. In 2010, cross-sectional data were also collected on these adolescents' mothers and fathers, friends, schools, and neighborhoods. In the proposed study, follow-up data will be collected from the original study participants, who are now young adults, and their parents, friends, and significant others. Additionally, data will be collected on the young adults' school/workplace and neighborhood environments. This longitudinal study will allow for an examination of how multiple factors predict changes in weight-related outcomes among diverse young people during key life course transitions involving new friendships, schools, living arrangements, roles, and responsibilities. The inclusion of longitudinal data collected directly from both mothers and fathers, or other caregivers as relevant, will help address unanswered questions about how parents can best help their adolescent and young adult children with weight-related problems, in a developmentally appropriate way, as they become more independent. Innovative research methodologies will be utilized to survey current friends and significant others of study participants and explore the potential impact of earlier, ongoing, and current friendships on weight- related outcomes over time. There is much to be learned about factors from within the domains of family, friend, school/workplace, and neighborhood environments and their relevance for weight-related outcomes. This comprehensive, longitudinal study will address new research questions that have emerged as key to understanding the etiology of weight-related problems in young people. Findings will guide the development of more innovative and effective interventions that target multiple environments of influence to prevent and treat a broad spectrum of weight-related problems in adolescents and young adults from diverse ethnic/racial and socio-economic backgrounds.